Liquid-cooled electric lamp



Patented Mar. 7, .1939

PATENT OFFICE 2 150,007 uoom ooonnn ELE-(HBIO mm 7 John W. Byde,Middlesex, England, nul -nor to I General Electric Company, acorporation of New York Application September 14, 1937, Serial No.163,835 In Great Britain September 21, 1936 30laims.

My invention relates to electric lamps and similar devices and moreparticularly to high-intensity electric lamps. Still'more particularlymy invention relates to means for cooling such lamps g by a liquid.

My invention is particularly adapted to, and will be described inconnection with, high pressure metallic vapor lamps of the typedisclosed and claimed in United States application Serial to No.-46,952, Cornelis Bol at al., filed October 26, 1935. Lamps of this type,having an envelope a few millimeters in diameter, have been cooledheretofore by placing them in a larger tube or jacket through whichwater is circulated. The

35 distance between the lamp envelope and the jacket was usually notless than flve millimeters and the surface of the lamp was not cooledadequately even though the rate of flow of the water was so great thatthere was no considerable rise 52% in its average temperature. Bubbleswere often formed at the heated surface which interfered greatly withthe primary use of the devices, namely as sources in optical projectionapparatus, and, also indicated that the surface of the enas velope wasnot cooled as well as it might be.

One of the objects of the present invention is to provide means forimproving the cooling without increasing the rate at which cooling fluidhas to be supplied or decreasing materially, by to absorption, the lightoutput of the lamp.

According to my invention, the cooling means comprises a jacketsurrounding. the discharge lamp so that fluid can be caused to flow overthe envelope of the lampgin a direction generally 35 parallel to thedischarge. One'or more partitions are so arranged in the jacket thatsubstantially all the fluid passes by a partition through a channelformed by the space between the partition and the lamp envelope, thecross section of said 40 channel being much less than the mean crosssection of the channel through which the fluid passes over the part ofthe envelope occupied by the discharge. It is to be observed that thelatter condition insures that the total length along the 45 dischargeoccupied by the partitions is small compared with the total length ofthe discharge. The effect of the partitions on the light emitted by thelamp is therefore small and they do not raise very greatly the pressurerequired to force a so given flow of water through the jacket. Theireflect in promoting cooling is doubtless due largely to the increasethey produce in the velocity of the stream along the surface of the lampenvelope, but it is probably also due to the pro- 55 motion ofturbulence. If light is to emerge, at

least part of the vessel must, of course, be of glass or like material,but if light is required in only one direction, a glass window may besuflicient. If the object were, as it might be, to expose the coolingliquid to radiation, the vessel. might be wholly opaque and, forexample, of metal. The use of the partitions, rather than of a tube asnarrow as the channel, enables a much smaller head of liquid to be usedand it makes occasional bubbles less harmful. Further fea- 1o tures andadvantages of my invention will appear from the following detaileddescription of species thereof and from the drawing.

In the drawing, Fig. l is a longitudinal sectional view of awater-cooled high pressure vapor. lamp comprising my invention, andFigs. 2 and 3 are side elevations of modifications with the coolingjacket in section.

Referring to Fig. l, the discharge lamp shown therein is of theextremely high pressure mercury type disclosed in the above-mentionedapplication of B01 et a1. and comprises a tubular quartz envelope lwhich may have, for example, an overall length of 80 mm, an externaldiameter of 6 mm. and an internal diameter of 2 mm. The are gap betweenthe electrodes 5, 8 may be 15 mm. and in operation the discharge maycarry one ampere at 800 volts. A tube or jacket 2, which may be of glassand have an internal diameter of 14 mm., is concentrically disposed 3around the envelope I, and water may be driven through the annularcooling chamber formed thereby from an inlet to an outlet not shown) atthe rate of about 2.5 litres per minute. Two

transverse partitions 3, l, each of which may 3 be one millimeter thickand leaves central aperture 8 mm. in diameter, obstruct the flow ofwater near each electrode and force it to flow through the channel onemillimeter wide between the partition and the envelope. The saidpartitions 3, l are shown as washeror ring-like discs which may besealed at their peripheries to the surface of the jacket 2. The saidpartitions may also be formed from the wall of the jacket 2 by pressingthe glass inward. It is important that there should be no considerablegap between .the partitions and the jacket through which the water mayflow; thus, metal discs fitting the jacket imperfectly were deflnitelyless satisfactory.

The upstream partition 3 should be (as shown in Fig.8) somewhat upstreamof the face of the upstream electrode 5. The downstream partition 4 isnot absolutely n and may be omitted, for it was found that even ii. onlyparevident on the surface of the envelope I when imperceptible. Howevethe partition 4 provides a factor of safety. If the distance between theelectrodes is more than 15 mm., more than two partitions may berequired. As a general rule it was found that the effect of eachpartition', such as is shown, persists for about 15 mm. on thedownstream side of it if the rate of now is that stated above.

The partitions need not be P pendicular to the surface of the envelopebut may be inclined, for example, as shown in Figs. 2 and 3.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The combination of an electric discharge lamp comprising a tubularenvelope having an electrode sealed in each end thereof, a tubularjacket surrounding said envelope and spaced therefrom to form an annularcooling chamber through which liquid can be caused to flow over saidenvelope, and a transversely extending partition in said cooling chamberlocated adjacent to the upstream electrodeand spaced from said envelopeto 'form a channel of much smaller cross section than the mean crosssection of the channel through which the liquid passes over the part ofthe envelope occupied by the discharge.

2,150,007 gtition 3 were present, the bubbles which were 2. Thecombination of an electric discharge lamp comprising a tubular envelopehaving an electrodesealed in each end thereof, a tubular jacketsurrounding said envelope and spaced therefrom to form an annularcooling chamber through which liquid can be caused to flow over saidenvelope, and a transversely extending par- 'tition in said coolingchamber located adjacent to each of said electrodes and spaced from saidenvelope to form a channel of much smaller cross section than the meancross section of the channel through which the liquid passes over thepart of the envelope occupied by the discharge. I

3. The combination of an electric discharge lamp comprising a tubularenvelope having an electrode sealed in each end thereof, a tubularjacket surrounding said envelope and spaced therefrom to form an annularcooling chamber through which liquid can be caused to flow over saidenvelope, and a transversely extending partition in said cooling chamberlocated adjacent to and upstream of the face of the upstream electrodeand spaced from said envelope to form a channel of much smaller crosssection than the mean cross section of the channel through which theliquid passes over the part of the envelope occupied by the discharge.

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